FEMA flood maps using old lake data

Agency to work with Corps of Engineers to collect current data

7/17/13

ARENAC COUNTY — The new preliminary flood plain maps that the Federal Emergency Management Agency plans to implement for Arenac County are using Great Lakes water level data from 1988.

Civil engineers and representatives from the FEMA and the Department of Environmental Quality showed the new maps July 10 at Omer City Hall to officials and the public. FEMA civil engineer Ken Hinterlong said the 1988 data was the most recent that FEMA has for Lake Huron, though he acknowledged it does not reflect the current water levels.

“The low (Great Lakes) water levels are not accounted for,” Hinterlong said. “We’re using 1988 data for the lakes.”

FEMA is planning on working with the U.S. Army Corps of Engineers to map the water levels more accurately over the next few years. These new lake level maps would account for historical data between 1960 and 2009, as well as additional LiDAR mapping. When those new maps are complete, the flood plain maps for Arenac County would be revised, Hinterlong said, adding that it could be three or four years before that happens.

Hinterlong said the new flood plain maps are part of a national program to update the topographical and flood maps across the entire country using new technology to get them as accurate as possible. The maps are based off of a U.S. Geological Survey 2010 LiDAR survey, where planes flew over the county and used laser pulses to determine elevations and topography. Hinterlong said those measurements are accurate to a margin of error of plus or minus 2 feet.

The Au Gres City Council expressed its displeasure with the new maps’ failure to account for low water levels in the Au Gres River and Saginaw Bay at its meeting July 2. The board believed the new flood plain maps will hurt new development in the city.

River systems such as the Rifle and Au Gres are trickier for FEMA to measure, as only the Rifle River has a National Weather Service marker — near Sterling — to determine when it hits flood stage. FEMA currently has no scheduled plans to update the river data itself, Hinterlong said, but FEMA is open to the local communities updating that information and submitting it themselves. Alternately, they could try and require FEMA to study the broader Saginaw Bay watershed.

The Arenac County Board of Commissioners could propose doing its own survey, as Gladwin County has, but municipalities within the county, including the county itself, would be on the hook to pay for it.

Before the flood plain maps are approved, Hinterlong said FEMA will have a 90-day appeals period, starting sometime around September. At this time, the agency will be seeking information to help refine the data for their own maps, including hydrological modeling data and topographical maps. It will also be taking appeals letters to address concerns of property owners.

Once the appeals period has closed and the letters are addressed, the maps will be finalized. Hinterlong believes they could be finished by the end of the year unless additional surveys are needed.

Mark Seidelmann, a civil engineer with STARR —a contractor company working with the DEQ and FEMA — said anything that could reduce water flow or flooding, such as wetlands or farm drains, needs to be accounted for in the maps.

“(These maps) are paramount for deciding what kind of land use can be done by the waterways,” Seidelmann said.

Hinterlong said the modern geological information study information is useful for planning and zoning needs, and that FEMA is obligated to update them. He insisted it was not about money, though people with property mortgages in a flood zone are required to get flood insurance.

Lincoln Township Supervisor David Hertzberg said he was told there were 69 flood claims in Arenac County in the past decade totaling a payout of $208,000. In contrast, premiums paid into totaled around $2 million.

FEMA will require that the townships each approve an ordinance that requires new building permits take the flood plain maps into account so property owners can get flood insurance.

“When the new maps are approved, we’re going to have to do an ordinance within six months,” Hertzberg said to his township board July 11. “When they expand the maps, we will be in it, all townships.”

Adams Township, Sterling and Twining have not had any flood zones identified under the new mapping, according to FEMA documentation released at the open house.

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